Drilling tool



Nov. 1, 1966 w. s. CAROTHERS 3,232,358

DRILLING TOOL Filed April 15, 1964 J36 INVENTOR.

WILLIS S. CAROTHERS his ATTORNEY United States Patent Ofilice 3,282,358Patented Nov. 1, 1966 Pennsylvania Filed Apr. 13, 1964, Ser. No. 359,291Claims. (Cl. 175-411) This invention relates to a drilling tool and moreparticularly to a junk mill for drilling hard formations, metal or otherobstructions from a well bore.

Those concerned with the development of oil well tools have longrecognized the need for drilling tools of various types for penetratinghard formations or drilling up objects lost or otherwise mispositionedin the bottom of a Well bore such as pieces of drill pipe, casing ortools which cannot be readily removed in any other manner. Most of themilling tools used for this purpose have been combined with a junkbasket and the mill has been of the coring variety where only aperipheral portion of the junk has been removed by milling leaving acentral or core portion to be removed by the action of the junk basket.Such devices have served the purpose under most circumstances and arestill being used with success when circumstances are such as to allowthe core portion to be retrieved Without being drilled up. However,under conditions that prevent retrieving the junk in a single piece itis necessary to completely drill up the junk, reducing it to fineparticles which can be removed from the hole by circulation of drillmud. Under such circumstances the milling tool of the present inventionis very useful since this milling tool comprises a plurality of cuttingsurfaces disposed at a variety of angles with respect to the axis of thewell bore and at least some of which extend more than half way acrossthe face of the mill so that no central or core portion of the junk isleft in the bore to be retrieved by a junk basket or like apparatus.

It is therefore an object of this invention to provide a new andimproved junk mill.

It is a further object of this invention to provide a new and improvedjunk mill having a cutting face with a plurality of cutter bladesthereon.

It is another object of this invention to provide a new and improvedjunk mill operable in a well bore and hav ing a cutting facesubstantially normal to the axis of such well bore with a plurality ofcutting surfaces arranged on the cutting face in a particular mannerthat provides cutting action over the whole area within the well bore.

It is still another object of this invention to provide a new andimproved junk mill having a plurality of cutting surfaces of variedlength and angular positioning so as to provide efficient cutting andsmooth nonchattering operation in drilling metallic objects or hardformations which obstruct the bore of a well being formed in earthstrata.

These and other objects and advantages of this invention will be morereadily apparent upon consideration of the following description anddrawings in which:

FIGURE 1 is an end elevational View of a junk mill constructed accordingto the principles of this invention with a portion broken away to showconstruction features;

FIGURE 2 is a sectional view taken substantially on line 22 of FIGURE 1;and

FIGURE 3 is a sectional view taken substantially on line 3-3 of FIGURE1.

Referring now to the drawings, in FIGURE 2 there is shown a portion of awell bore 6 being formed in earth strata by ordinary drilling methodswherein at least a portion of the bore 6 is lined with a casing 8 of atype well known in the art. Within the casing 8 there I is shown afragmentary portion of the box end 10 of a drill pipe or tool jointsuspended within the casing 8 in the usual manner for axial movementwithin the casing 8 and powered for rotation about the axis 9 of thecasing 8 in a manner well known in the art. The box end 10 is providedwith tapered internal threads which mate with and threadedly engageupwardly tapering external threads 12 on an upper portion 11 of a junkmill 15 constructed according to the principles of this invention. Thejunk mill 15 comprises an axially elongated, hollow, generallycylindrical mill body member 14 having a nearly flat bottom face portion16 substantially normal to the axis of the casing 8 at the bottom end ofthe body member 14. Extending radially outward from the body portion 14is a plurality (shown as 5) of axially elongated guide members 18extending from a point downwardly adjacent the upper portion 11 to asubstantial distance below the face portion 16. The guide members 18have axially extending arcuate surfaces forming portions of theperiphery of a circle having a diameter slightly smaller than the insidediameter of the casing 8 so that the guide members 18 provide for asmooth rotation of the junk mill 15 within the casing 8. The downwardlyextended portions of the guide members 18 provide mounting surfaces,hereinafter described, for cutting elements mounted at the bottom end ofthe junk mill 15.

Extending downwardly within the body portion 14 for approximately halfits length is an axial bore 20 which widens into an enlarged axialcavity 22 extending downwardly within the body portion 14 approximatelyanother third of the length of the body portion 14 which cavity 22communicates with the face portion 16 through a plurality of bores 24(see FIGURE 1). At its upper end the axial bore 20 communicates with thecentral bore of the box end 10 which in turn communicates at the upperend of the well with a source of pressurized fluid such as drill mud asis well known in the art. The bore 20, the cavity 22 and the bores 24together with the spaces between the guide members 18 provide for fluidcirculation to remove solid particles formed in the milling operation.

The portion of each guide member 18 which extends downwardly beyond theface portion 16 forms a cutter support 19 having a fiat rearward face 26parallel to the axis of the casing 8, terminating in an edge 27 sub-:stantially parallel to end surface 16 and an upwardly stepped forwardface 28 (see FIGURE 3) forming a series of alternating horizontal andvertical surfaces 29 and 29' respectively. A matrix 30 of material suchas brass or other soft metal in which is mixed a quantity of coarseparticles 32 of a very hard material such as sintered tungsten carbideor the like is deposited on, and bonded to, the surfaces 29 and 29forming a cutter element 33 on each cutter support 19. One suitablematerial for this purpose is Kutrite mill formula which is a registeredtrademark of the B & W Metals Company, Inc. of Houston, Texas and issupplied in the form of rods or separate sintered particles of varioussizes. The embedded particles 32 and the matrix 30 are, of course, notlimited to the Kutrite formula but can be any particles, of suitablesize and hardness for the conditions to be encountered in the millingoperation, embedded in a suitable matrix. The direction of rotation ofthe junk mill 15 being counterclockwise as viewed in FIG- URE 1 and fromright to left as viewed in FIGURE 3 and shown by the arrows 34, thestairstep design of the forward face 28 provides back-up support andreinforcement for the matrix 30 and the particles 32 comprising thecutter elements or blades 33 when the mill 15 is being operated ashereinafter described.

It is to be noted that the rearward faces 26 of the cut ter supportelements 19 are not radial to the axis 9 but are portions of planesparallel to the axis 9 at varying distances from the axis 9 so that theorientation of the surfaces 26 is random and provides random spacingbetween the various cutter elements 33. The rearward faces also vary inchordal length and in axial dimension with the faces of shorter chordallength having greater axial dimensions so that the smallest of thecutter elements 33 becomes the leading element of the series of cuttersand the largest cutter is the final element of the series. At least oneof the cutter supports 19 extends across the surface 16 beyond the axis9 to provide full cutting action over the cross sectional area withinthe casing 8.

The outer surfaces of the cutter support elements 19 and small adjacentportions of the respective guide members 18 are of a reduced diameter toallow for the deposition of a layer 36 of finely divided tungstencarbide or other hard particles on the outside of the cutter supportelements 19 and the lower portion of the guide members 18 to assure thatthe mill 15 will provide clearance for the remaining portions of theguide members 18 as it progresses downwardly in the cutting operation.

In operating the junk mill 15 of this invention the mill 15 isthreadedly secured on the lower end of a drill string and lowered into awell casing in the usual manner. The guide members 18 being of a size toslide readily through the casing 8 until an obstruction in bore 6 isreached.

When the cutting surfaces approach the obstruction, rotation is appliedto the drill string and mill 15 in the usual manner while the mill isstill above the obstruction in the well bore 6. As the mill continuesdownward the particles 32 begin to contact the obstructing material asfor instance metal objects with the smallest of the blades or cutterelements 33 making the first contact. The small blade removes a portionof the material and is followed by larger and larger blades contactingthe obstructing material as the mill 15 progresses downwardly. Thenon-radial orientation of the blades in addition to the variations inaxial dimension and chordal length provide a very good cutting actionwith superior penetration and smoother cutting than is obtainable byknown cutters of the prior art wherein the blades are radial and ofequal chordal length and axial dimension.

Other advantages of the present invention reside in the provision of themassive cutting elements 33 containing the relatively small sharp edgedparticles 32 of extremely hard material with the cutting elements 33sup-ported and reinforced by the backup stair step design of the cuttersupport elements 19 as well as by the massive one-piece design of thebody member 14 and the guide members 18 with no separate piecessusceptible of being loosened or damaged by vibration inherent in thecutting action, such vibration being especially troublesome when oddshaped pieces of junk are being encountered. With such design heavy feedpressure can be used resulting in rapid cutting with a concomitantsaving in job time.

A further advantageous feature of this design is that the elongated,radially extended guide members 18 can be machined to fit a variety ofcasing sizes without Change in the body member 14 and without losing theadvantage of random positioning and non-radial orientation describedabove. Such machining can include the complete removal of the guidemembers 18 leaving the cutter support elements 19 extending only fromthe end surface 16 without departing from the principles of thisinvention.

It is to be realized that a preferred embodiment of the presentinvention has been described and illustrated herein. However, otherforms of this invention are possible and envisioned for the future. Itis therefore respectfully requested that this invention be interpretedas broadly as possible and be limited only by the prior art.

In practice the bottom face portion 16 has been made as afrusto-conical, concave surface and can be convex to flat to suitparticular situations.

I claim:

1. A milling tool for rotation within a well bore comprising: anelongated body member having an end surface substantially normal to theaxis of rotation of said body member; said body member having aplurality of cutter support members extending axially at least in partfrom said end surface, said cutter support members having rear surfaceswith respect to a direction in which said body member is rotated, saidrear surfaces extending from said end surfaces and terminating in outeredges substantially parallel to said end surface, said cutter supportmembers extending chordally across respective portions of said endsurface, at least some of said edges being of nonradial orientation withrespect to said axis, said cutter support members having forward areaswith respect to said direction of rotation extending generally inwardlyfrom said outer edges and forwardly to said end surface; and cuttermeans formed upon and bonded to each of said forward areas.

2. A milling tool as specified in claim 1 wherein said cutter meanscomprises a relatively soft matrix having relatively hard particlesembedded therein.

3. A milling tool as specified in claim 1 wherein said cutter supportmembers differ in chordal length.

4. A milling tool as specified in claim 3 wherein those of said cuttersupport members having greater chordal lengths have lesser axialdimensions.

5. A milling tool for rotation within a well bore comprising: anelongated body member having an end surface substantially normal to theaxis of rotation of said body member; said body member having aplurality of cutter support members extending axially at least in partfrom said end surface, said cutter support members having rear surfaceswith respect to a direction in which said body member is rotated, saidrear surfaces extending from said end surface and terminating in outeredges substantially parallel to said end surface, said cutter supportmembers extending chordally across respective portions of said endsurface, at least one of said cutter support members extending more thanhalf way across said end surface, and at least some of said edges beingof nonradial orientation with respect to said axis, said cutter supportmembers having forward areas with respect to said direction of rotationextending generally inwardly from said outer edges and forwardly to saidend surface; and cutter means formed upon and bonded to each of saidforward areas.

6. A milling tool for rotation within a well bore comprising: anelongated body member having an end surface substantially normal to theaxis of rotation of said body member; said body member having aplurality of cutter support members extending axially at least in partfrom said end surface, said cutter support members having rear surfaceswith respect to a direction in which said body member is rotated, saidrear surfaces extending from said end surface and terminating in outeredges substantially parallel to said end surface, said cutter supportmembers having different axial lengths and extending chordally acrossrespective portions of said end surface, at least some of said edgesbeing of non-radial orientation with respect to said axis, said cuttersupport members having forward areas with respect to said direction ofrotation extending generally inwardly from said outer edges andforwardly to said end surface, and cutter means formed upon and bondedto each of said forward areas.

7. A milling tool as specified in claim 6 wherein at least one of saidcutter support members extends more than halfway across said endsurface.

8. A milling tool for rotation within a well bore comprising; anelongated body member having an end surface substantially normal to theaxis of rotation of said body member. elongated guide members extendingradially out wa-rdly from said body member, each said guide memberextending axially along said body member from an intermediate portion ofsaid body member to a line substantially beyond said end surface andsubstantially parallel to said end surface to form a cutter supportmember, said cutter support members having planar rear surfaces withrespect to the direction of such rotation said rear surfaces extendingfrom said line to said end surface and being portions of planes parallelto said axis, said cutter support members extending across respectiveportions of said end surface and at least some of said rear surf-acesbeing of non-radial orientation with respect to said axis, said cuttersupport members having stepped front surfaces extending forwardly insteps from said line to said end surface, and cutter means formed uponand bonded to each of said cutter support members.

9. A milling tool for rotation within a well bore comprising: anelongated generally cylindrical body member having an end surfacesubstantially normal to the axis of rotation of said body member; aplurality of circumferentially spaced, elongated guide members extendingradially outward from said body member; each said guide member extendingaxially along said body member from an intermediate portion of said bodymember to a line substantially beyond said end surface and substantiallyparallel to said end surface to form a cutter support member, saidcutter support members having planar rear surfaces with respect to thedirection of such rotation, said rear surfaces extending from said lineto said end surface and being portions of planes parallel to said axis,said cutter support members extending across respective portions of saidend surface, at least some of said rear surfaces being of non-radialorientation with respect to said axis, said cutter support membershaving stepped front surfaces extending forwardly in steps from saidline to said end surface; a cutter element formed upon and bonded toeach of said cutter support members, each said cutter element comprisinga relatively soft matrix having relatively hard particles embeddedtherein.

10. A milling tool for rotation Within a well bore comprising: anelongated generally cylindrical body member having an end surf-acesubstantially normal to the axis of rotation of said body member; aplurality of circumferentially spaced, elongated guide members extendingradially outward from said body member; each said guide member extendingaxially along said body member from an intermediate portion of said bodymember to a line substan tially beyond said end surface andsubstantially parallel to said end surface to form a cutter supportmember, said cutter support members having planar rear surfaces withrespect to the direction of such rotation, said rear surfaces extendingfrom said line to said end surface and being portions of planes parallelto said axis, said cutter support members extending across respectiveportions of said end surface, and having random chordal lengths andaxial dimensions wherein the support members of shorter chordal lengthhave greater axial dimensions than the support members of greaterchordal lengths, at least some of said rear surfaces being of non-radialorientation with respect to said axis, said cutter support membershaving stepped front surfaces extending forwardly in steps from saidline to said end surface; a cutter element formed upon and bonded toeach of said cutter support members, each said cutter element comprisinga relatively soft matrix having relatively hard particles embeddedtherein.

References Cited by the Examiner UNITED STATES PATENTS 2,507,222 5/1950Phipps 4l8 X 2,855,994 10/1958 Kammerer 175411 X 3,127,945 4/1964Bridwell 175-329 3,163,244 12/1964 Zimmerman 175398 CHARLES E. OCONNELL,Primary Examiner.

N. C. BYERS, Assistant Examiner.

1. A MILLING TOOL FOR ROTATION WITHIN A WELL BORE COMPRISING; ANELONGATED BODY MEMBER HAVING AN END SURFACE SUBSTANTIALLY NORMAL TO THEAXIS OF ROTATION OF SAID BODY MEMBER; SAID BODY MEMBER HAVING APLURALITY OF CUTTER SUPPORT MEMBERS EXTENDING AXIALLY AT LEAST IN PARTFORM SAID END SURFACE, SAID CUTTER SUPPORT MEMBERS HAVING REAR SURFACESWITH RESPECT TO A DIRECTION IN WHICH SAID BODY MEMBER IS ROTATED, SAIDREAR SURFACES EXTENDING FROM SAID END SURFACES AND TERMINATING IN OUTEREDGES SUBSTANTIALLY PARALLEL TO SAID END SURFACE, SAID CUTTER SUPPORTMEMBERS EXTENDING CHORDALLY ACROSS RESPECTIVE PORTIONS OF SAID ENDSURFACE, AT LEAST SOME OF SAID EDGES BEING OF NONRADIAL ORIENTATION WITHRESPECT TO SAID AXIS, SAID CUTTER SUPPORT MEMBERS HAVING FORWARD AREASWITH RESPECT TO SAID DIRECTION OF ROTATION EXTENDING GENERALLY INWARDLYFORM SAID OUTER EDGES AND FORWARDLY TO SAID END SURFACE; AND CUTTERMEANS FORMED UPON AND BONDED TO EACH OF SAID FORWARD AREAS.